1. Technical Field of the Invention
This invention pertains generally to fluid flow and control using a pinch valve. More specifically, the invention pertains to a pinch valve having an air-to-open pneumatic chamber which is in a closed position at rest, a removable headpiece, and a plunger configured to reduce damage to tubing which is repeatedly pinched in the valve.
2. Background of the Invention
Complex flow control systems are a common element in process and manufacturing systems, particularly in bio-process and bio-manufacturing. In such systems, it is important to carefully control process parameters such as flow rates, temperatures, pH, dissolved oxygen levels, sterility and fluid makeup, to name a few. As such, fluid control systems and valves which can provide rapid and accurate control of fluids in a sterile manner are highly sought after.
Pinch valves are typically a full bore or fully ported type of control valve which uses a pinching effect to obstruct fluid flow in a flexible tube. Such systems require that the tubing in the system is cut or that connections are broken to install the valve in place. Sterility and operation performance are consequently compromised. Further, many pinch valves are controlled by pneumatic means using compressed air to actuate the pinching mechanism and stop fluid flow within the flexible tube. In the event of power failure or loss of air pressure, the failure mode for many such valves is open. For systems which have a closed failure mode, repeated pinching of the flexible tubing frequently leads to tube damage and/or tube breakage. In systems which circulate corrosive or unstable fluids, or when material compatibility or contamination with the product is a factor in the application, both failure modes represent large risks.
Accordingly, there exists a need in the prior art for a pneumatic pinch valve with a pure closed fail mode, which may be installed onto an existing system without breaking any connections, and which may be actuated repeatedly without causing tube damage.